The specific aims of this project is to study the number and composition of the subunits of the native and of the insoluble gelatinous mucin which will be isolated from porcine gastric mucosal secretions of single donor animals. The amino acid sequence of the subunits and the reaggregation properties of the subunits will also be studied. The experimental design includes isolation and purification water insoluble gelatinous (gel) mucoprotein subunits by molecular sieve chromatography, accessing the number and size of the subunits by HPLC, and density gradient centrifugation, conformation of the number of subunits by electrophoresis, the utilization of proteolytic enzymes as tools of structural analysis, determination of the amino acid composition and sequence of the purified mucin subunits. The protective function of the mucosal secretions lies in the composition and the molecular interactions involved in the gel-forming and viscous properties of mucus. It appears that any changes in the physical and/or chemical properties of the mucosal layer may likely contribute to, or be an indicator of, a diseased state. The protective function of the mucus blanket has been indicated in disease states such as gastric ulceration, colitis, chronic bronchitis, asthma and gastritis. We propose to acquire a more precise definition of structural relationships of the mucus components and add to the body of knowledge of the role mucus structure in normal and diseased states.